The primary purpose of the commonly used cosmetics for makeup is to cover skin defects, provide transparency and brightness to the skin, protect the skin from ultraviolet (UV) rays, control sweat and sebum, or the like, thereby cleansing and protecting the skin and providing satisfaction. Various inorganic powders such as titanium dioxide, sericite, etc. are used in the cosmetic compositions for makeup for as UV block agent and pigment. However, these inorganic powders are disadvantageous in that they exhibit poor usability because of crystallinity or rough surface and dispersibility is remarkably reduced because of inter-particle aggregation. Accordingly, there have been many attempts of surface treatment of inorganic powder for use in cosmetic compositions to improve dispersibility and rough usability of the inorganic powder.
Until recently, skin-friendly materials have been physically adsorbed on the surface of inorganic powders for the purpose of such surface treatment. However, there are not many skin-friendly materials available and the weak physical treatment often leads to non-uniform surface treatment.
Accordingly, methods of chemically treating the surface of inorganic powders are attempted recently. For example, a method of directly grafting the biocompatible lipid-polymer 2-methacryloyloxyethylphosphorylcholine (MPC) on the surface of silica using a coupling agent having an isocyanate functional group (European Polymer Journal 42 (2006) 3221-3229) and a method of coating MPC on the surface of titanium dioxide using trichloroacetyl chloride (Korean Patent Application No. 10-2012-0065929) were reported. However, these methods are disadvantageous in that they require use of a metal catalyst such as molybdenum, use of toxic solvents such as toluene is necessary and a process of removing salts produced during the reaction has to be added. Therefore, an economical, ecofriendly and simple process for uniformly coating the surface of an inorganic powder is necessary.